The present invention relates to a process for preparing a hydrogenated product of a cyclic olefin ring-opening metathesis polymer.
The hydrogenated products of a cyclic olefin ring-opening metathesis polymer and copolymer have attracted attention as resins having excellent optical and electric properties, high rigidity, heat resistance and weather-tightness. Therefore, many processes for preparing various ring-opening metathesis polymers and hydrogenated products of the polymers have been proposed.
Some processes for hydrogenating carbon-carbon double bonds in the main chain of a cyclic olefin ring-opening metathesis polymer are known. For example, heterogeneous catalysts that are metal-supported catalysts are used. In the catalysts, a metal such as palladium, platinum, rhodium, ruthenium or nickel is supported on a carrier such as carbon, silica, alumina, titania, magnesia., diatomaceous earth and synthetic zeolite. JP-A-3-174406 (Tokkaihei) and JP-A-4-363312 (Tokkaihei) each disclose a process in which some of these catalysts are used to hydrogenate ring-opening metathesis polymers.
In homogeneous catalysts, nickel naphthenate/triethylaluminum, nickel acetylacetonate/triisobutylaluminum, cobalt octenate/n-butyllithium, titanocene/diethylaluminummonochloride, rhodium acetate, dichlorobis (triphenylphosphine)palladium, chlorohydridocarbonyltris(triphenylphosphine)ruthenium or chlorotris(triphenylphosphine)rhodium is used. JP-A-5-239124 (Tokkaihei) and JP-A-7-41549 (Tokkaihei) each disclose a process in which some of these catalysts are used to hydrogenate ring-opening polymers.
However, the hydrogenation reaction is heterogeneous when a metal-supported catalyst is used. Therefore, there is a problem in that such catalyst is used in large quantities to obtain high hydrogenation rate. On the other hand, the homogeneous catalyst has a property that the hydrogenation reaction proceeds even when small amounts of the catalyst are used. However, the Ziegler catalysts consisting of an organic salt of nickel, cobalt or titanium and an organometallic compound containing a metal such as aluminum, lithium, magnesium or tin are deactivated by water, air or polar compounds. Therefore, there is a problem in that the treatment is complex and a solvent having large polarity can not be used.
Furthermore, there is a problem in that metallic complexes such as a complex of rhodium are expensive and their activity is not always high enough. These catalysts have a large steric hindrance to, for example, the hydrogenation of a cyclic olefin ring-opening metathesis polymer because there is a bulky tricyclododecenoic ring in the neighborhood of the carbon-carbon double bond in the ring-opening metathesis polymer. Therefore, it has been considered that it is difficult to hydrogenate the polymer in high hydrogenation rate. Especially it has been considered that it is difficult to hydrogenate the polymer in high hydrogenation rate when there are polar substituents such as hydroxyl, carbonyl, carboxyl, and nitrile groups in the ring-opening metathesis polymer.
Therefore, there have been demands for processes in which hydrogenation is easily carried out in high hydrogen conversion even in a cyclic olefin ring-opening metathesis polymer having a polar substituent such as nitrile group.